1. Field of the Invention
This invention relates to a color copier which makes use of the transfer thermal printing technique.
2. Description of the Prior Art
Among the color copiers developed to data are included xerographic printers.
The color copiers of this type have entailed a disadvantage that they need maintenance because their corotrons are susceptible of defilement and their photoreceptors are prone to gather dirt. They have suffered from a further disadvantage that attendant treatments such as compilation of images are difficult because the whole process ranging from the reading of an image on a given manuscript to the reproduction of the image is optically performed. They have a salient drawback that their machines proper take up large spaces and their power consumption is heavy because their fixing units spend much electric power.
Some other conventional color copiers are constructed as illustrated in FIG. 1 and FIG. 2. In a color copier of this construction, a thermal recording head 301 and an opposite roll 303 are disposed as opposed to each other and an ink donor film 302 is passed between them.
The ink donor film 302 has yellow, cyan, and magenta ink layers 310, 320, 330 applied cyclically repeatedly in the order mentioned on a substrate of the ink donor film 302 as illustrated in FIG. 2 throughout the entire length of the film. The length l of each of the ink layers of different colors is equalized to the circumferential length of the aforementioned opposite roll 303. This ink donor film 302 is taken up on a winding roll 307. The speed at which the ink donor film 302 is taken up on the winding roll 307 is equalized to the peripheral speed of the opposite roll 303.
The opposite roll 303 is provided with a retainer clip 304 adapted to keep hold of a recording paper 306 wrapped on the circumferential surface of the opposite roll 303. In the proximity of the circumferential surface of the opposite roll 303, a combination strip finger and paper pass guide 305 is disposed.
The conventional color copier thus constructed is operated as follows. The recording paper 306 is passed through the combination strip finger and paper pass guide 305 and wrapped around the opposite roll 303. Then, the recording paper 306 is fastened to the circumferential surface of the opposite roll 303 with the retainer clip 304. Subsequently, the yellow portion 310 of the ink donor film 302 is brought into contact with the recording paper 306 wrapped around the circumferential surface of the opposite roll 303 and, during one complete rotation of the opposite roll 303, a yellow image is recorded on the recording paper 306 by means of the thermal recording head 301.
After that, the cyan portion 320 of the aforementioned ink donor film 302 is brought into contact with the aforementioned recording paper 306 and the aforementioned opposite roll 303 is completely rotated once again to have a cyan image recorded by virtue of the thermal recording head 301.
Then, the procedure described above is repeated to superimpose the magenta portion 330 on the recording paper 306.
When the ink donor film is formed by using the three colors of yellow, cyan, and magenta as described above, one round of color recording is completed by applying three cycles of image information to the thermal recording head 301 and causing the opposite roll 303 to make three complete rotations. As the recording is completed, the retainer clip 304 holding the recording paper 306 in place is released and the combination strip finger and paper pass guide 305 is actuated to peel the recording paper 306 from the opposite roll 303. Thus, the recording paper 306 is removed.
Since the conventional color copier described above requires the recording paper to be wrapped around the opposite roll and then fastened to the circumferential surface of the opposite roll by means of the retainer clip, it has a disadvantage that the opposite roll is intricate in mechanism and the operation of recording is complicated. It has another disadvantage that the copying is not performed quickly because completion of one copy of color record requires three complete rotations of the opposite roll. It has yet another disadvantage that since the ink donor film must be produced by cyclically repeating three ink layers of dissimilar colors each in a length exactly equaling the circumferential length of the opposite roll, the ink donor film is difficult to fabricate and, consequently, costs dearly.